Two recognizable constellations of findings, a solid signet-ring cell pattern and a mucinous cribriform pattern, are present at least focally in the majority (78%) of ALK-positive tumors, but are rare (1%) in ALK-negative tumors.

Characteristic histologies are present both in primary sites and in metastases. Thus, histologic findings may help to identify cases for ALK testing.

ALK-positive cancers commonly showed coexpression of thyroid transcription factor-1 and p63, and its significance is currently unclear.

Chromosomal rearrangements leading to constitutive activation of anaplastic lymphoma receptor tyrosine kinase (ALK) define a category of lung adenocarcinomas that may be amenable to targeted therapy with the ALK inhibitor crizotinib.